1. Field of the Invention
This invention relates generally to a washing machine comprising a rotatable tub accommodating laundry with water at a wash step and rotated at high speeds at a dehydration step for dehydration, an agitator for agitating water in the rotatable tub, and an electric motor for driving the rotatable tub and the agitator, and more particularly to such a washing machine with a switching mechanism connecting the rotatable tub to a rotational system of the motor at the dehydration step and restricting the rotatable tub at the wash step and a rinse step, and a method of controlling the washing machine.
2. Description of the Prior Art
In conventional washing machines of the above-described type, a rotatable tub is connected to a hollow tub shaft rotatably mounted on a base member on which a mechanism section is further mounted. A washing shaft connected to an agitator disposed in the rotatable tub extends through a tub shaft. A drive switching mechanism such as a clutch mechanism is provided for transmitting a rotating force of a single electric motor selectively to the tub shaft or the washing shaft.
In a dehydration step, the tub shaft of the rotatable tub is engaged with a member of a rotation system of the motor by the clutch so that the rotatable tub is rotated at high speeds. In a wash step and a rinse step, the clutch is engaged with a restricting engagement portion provided on a base member stationary relative to the rotatable tub so that the tub shaft is connected via the clutch to the base member, whereby free rotation of the rotatable tub is restricted.
However, the clutch is sometimes engaged with a small rugged portion of the base member other than the restricting engagement portion prior to the start of the wash or rinse step. A sufficient restricting force cannot be obtained for the rotatable tub when the clutch is engaged with an irregular portion as described above. As a result, since the rotatable tub is rotated with water flows caused by the agitator in the wash or rinse step, a laundry agitating effect is reduced. Circularly arranging a number of restricting engagement portions would be suggested as a solution of the above-described problem. However, this solution renders the mechanical structure of the clutch large and complicated.